1. Field of the Invention
The present invention relates to a substrate that constitutes an ink jet head (hereinafter, simply referred to as an ink jet head) for discharging functional liquid, such as ink, onto recording media including paper sheet, plastic sheet, cloth, commodity, and the like, to record and print characters, symbols, images, and the like, while executing related operations. The invention also relates to an ink jet head formed by use of this substrate, and an ink jet pen that includes an ink reservoir unit to retain ink to be supplied to the ink jet head, as well as an ink jet apparatus having the ink jet head mounted on it.
In this respect, the ink jet pen referred to in the description of the present invention means to include a cartridge mode where the ink jet head and the ink reservoir unit are integrally formed, and a mode where the ink jet head and the ink reservoir unit are formed separately and detachably combined for use. The ink jet pen is structured to be detachably mountable on mounting means of the carriage or the like on the apparatus main body side.
Also, the ink jet recording apparatus referred to in the description of the present invention means to include a mode where it is formed integrally with or separately from a word processor, a computer, or some other information processing apparatus as its output device, and various modes where it operates as a copying system being combined with an information reader or the like, as a facsimile equipment having the functions of receiving and transmitting information, as a textile printing machine, or the like.
2. Related Background Art
An ink jet recording apparatus of the kind is characterized in that it discharges ink from the discharge opening as fine droplets for recording highly precise images at high speeds. Particularly, the ink jet recording apparatus of the type that it uses electrothermal transducing devices as energy generating means for generating energy to be utilized for discharging ink has, in recent years, attracted more attention, because it operates more suitably for recording images in higher precision at higher speeds, while making the recording head and apparatuses smaller, and also, making them more suitable for recording in colors. (For example, refer to the specifications of U.S. Pat. Nos. 4,723,129 and 4,740,796.)
FIG. 1 is a view which shows the general structure of the principal part of the head substrate used for an ink jet recording head described above. FIG. 2 is a cross-sectional view which schematically shows the ink jet recording head substrate 2000 on the part corresponding to the ink flow path, taken along line 2xe2x80x942 in FIG. 1.
In FIG. 1, the ink jet recording head is provided with a plurality of discharge openings 1001. Also, on the substrate 1004, the electrothermal transducing devices 1002 that generate thermal energy to be utilized for discharging ink from these openings are arranged for each ink flow path 1003, respectively. Each of the electrothermal transducing devices is formed mainly by the heat generating member 1005, the electrode wiring 1006 that supplies electric power to it, and an insulation film 1007 that protects them.
Also, each of the ink flow paths 1003 is formed by a ceiling plate having a plurality of flow path walls 1008, which is adhesively bonded, while its relative positions to the electrothermal transducing devices and others on the substrate 1004 are adjusted by means of image processing or the like. The end of each of the ink flow paths 1003 on the side opposite to the discharge opening 1001 is conductively connected with a common liquid chamber 1009. In this common liquid chamber 1009, ink supplied from an ink tank (not shown) is retained.
Ink supplied to the common liquid chamber 1009 is conducted to each of the ink flow paths 1003 from the chamber, and it is held in the vicinity of each discharge opening by means of meniscus that ink forms in such portion. At this juncture, when the electrothermal transducing devices are selectively driven, ink on the heat activation surface is abruptly heated to bring about film boiling by the utilization of thermal energy thus generated. Ink is discharged by means of its impulsive force at that time.
In FIG. 2, a reference numeral 2001 designates a silicon substrate, and 2002, a heat accumulation layer.
A reference numeral 2003 designates a SiO film that dually functions to accumulate heat; 1004, a heat generating resistive layer; 2005, a metal wiring formed by Al, Alxe2x80x94Si, Alxe2x80x94Cu, or the like; and 2006, a protection layer formed by SiO film, SiN film, or the like. Also, a reference numeral 2007 designates a anti-cavitation film that protects the protection film 2006 from the chemical and physical shock following the heat generation of the heat generating resistive layer 2004, and 2008, the heat activating portion of the heat generating resistive layer 2004.
For the heat generating member used for the recording head of an ink jet recording apparatus, it is required to provide the following characteristics:
(1) As a heat generating member, it should have an excellent capability of responding to heat, thus making it possible to discharge ink instantaneously.
(2) It has a smaller amount of change in resistance values with respect to the high speed and continuous driving, thus presenting a stabilized state of ink foaming.
(3) It has an excellent capability of heat resistance and heat response, as well as a longer life with high reliability.
There is disclosed in Japanese Patent Application Laid-Open No. 7-125218, a structure that uses TaN film for the material of a heat generating member as the one for an ink jet head that satisfies these requirements. The characteristic stability of the TaN film (that is, the ratio of resistance changes, in particular, when recording is repeated for a long time) is closely correlated with the composition of the TaN film. Particularly, the heat generating member formed by tantalum nitride containing TaN0.8hex has a smaller ratio of resistance changes when recording is repeated for a long time, and presents an excellent stability of discharges.
Incidentally, besides the ink jet recording head that uses such heat generating member, there is a thermal printing head that also uses a heat generating member to be directly in contact with a thermo-sensitive sheet or an ink ribbon for recording.
As the heat generating member for such a thermal printing head, there is, for example, the one which is disclosed in the specification of Japanese Patent Application Laid-Open No. 53-25442. This head has an excellent life characteristic as a heat generating member when it operates to generate heat at high temperature. This member is formed by at least one kind of the first element selected from among Ti, Zr, Hf, V, Nb, Ta, W, and Mo; by the second element of N, and by the third element of Si, while being composed by the first element at 5 to 40 atomic %; the second element, at 30 to 60 atomic %; and the third element, at 30 to 60 atomic %. Or as disclosed in the specification of Japanese Patent Application Laid-Open No. 61-100476, there is one heat generating member having highly thermal stability and excellent printing quality, which is formed by an alloy of tantalum, high fusion point metal (such as Ti, Zr, Hf, V, Nb, Cr, Mo, or W) and nitrogen. Further, as disclosed in the specification of Japanese Patent Application Laid-Open No. 56-89578, there is a thermal head that uses a heat generating member having an excellent acid-proof capability and stability of resistance values, which contains the metal that forms nitride, silicon, and nitrogen. Also, as disclosed in the specification of Japanese Patent Publication No. 2-6201, there is a thermal head using Taxe2x80x94Sixe2x80x94O thin film as the heat generating member, which has durability against high speed recording as well as against the use that requires a long life of the member.
At present, however, HfB2, TaN, TaAl or TaSi is used as material for the heat generating member for an ink jet recording head. Here, in general, none of the heat generating members adopted for the thermal printing head described above is practically used for the ink jet recording head.
This is due to the fact that whereas an electric power of approximately 1 W is applied to the heat generating member of the thermal printing head per 1 msec, an electric power of approximately 3 to 4 W is applied to the heat generating member of the ink jet head per 7 xcexcsec, for instance, which is larger than the electric power given to the thermal printing head by several times. Therefore, the heat generating member of the ink jet head tends to receive more thermal stress than the thermal printing head in a shorter period of time.
Consequently, for such heat generating member, it is necessary to consider the discharge and method for driving the member genuine to an ink jet head, which are different from the method adopted for the thermal printing head. Thus, the design consideration should be given to the heat generating member (with respect to the film thickness, heater size, configuration, and the like) optimized for use of the ink jet head. It is impossible to adopt a heat generating member currently in use for a thermal printing head for the ink jet head as it is.
Now, for the ink jet recording apparatus, there has been demand, in recent years, on the enhancement of its functions with respect to the production of higher image quality and higher recording speeds as described earlier. Here, in order to make the image quality higher, there is a method of improving the image quality by making the size of each heater (heat generating member) smaller so that the discharge amount is reduced per dot to obtain small dots as intended.
Also, for the performance of a higher recording, there is a method of increasing driving frequency as required by making pulses shorter still than conventionally practicable.
Nevertheless, in order to drive the heater at higher frequency in a structure where the heater size is made smaller for the purpose of obtaining higher image quality as described above, the sheet resistance value thereof should be made larger. FIG. 3A is a graph which illustrates the relations between various driving conditions depending on the difference in heater sizes.
FIG. 3A shows changes of the sheet resistance value of the heat generating member and electric current value with respect to the pulse width when the heater size changes from larger (A) to smaller one (B) at a constant driving voltage. Likewise, FIG. 3B is a graph which illustrates the relations between the sheet resistance value of the heat generating member and the electric current value with respect to the driving voltage when the heater size changes at a constant width of driving pulse.
In other words, when the heater size is made smaller, it is necessary to increase the sheet resistance value in order to drive the member under the same condition as conventionally practicable. Also, with energy requirement in view, it is possible to reduce the electric current value when the sheet resistance value is made larger, and the member is driven at a higher driving voltage, hence attaining energy saving. Such effect becomes significant particularly when the structure is such that a plurality of heat generating members are arranged.
As described earlier, however, the specific resistance value of the heat generating member formed by HfB2, TaN, TaAl, or TaSi, among some others, used for the ink jet recording head currently in use is approximately 200 to 300 xcexcxcexa9xc2x7cm. Therefore, in consideration of the stability of heat generating members being produced, the stabilized characteristics of discharges, and the like, the limit of the sheet resistance value is 150 xcexa9/xe2x96xa1 if the limit of the film thickness of the heat generating member is considered to be 200 xc3x85.
Therefore, if it is intended to obtain a larger value of sheet resistance than such limit, it becomes difficult to use any one of the heat generating members described above.
In the meantime, the heat generating member adopted for the thermal printing head described above makes it possible to increase the sheet resistance value. However, it is impossible to adopt such member for the ink jet head that requires the attainment of the particular heat response and high speed performance of recording as described above.
Further, for an ink jet recording apparatus, the power source capacitance and the semiconductor device should withstand pressure. As a result, there is automatically limit to the driving voltage. It is currently considered that the upper limit thereof is approximately 30 V. In order to drive the apparatus at a driving voltage less than this limit, it is necessary to set the specific resistance value of the heat generating member at 4,000 xcexcxcexa9xc2x7cm or less. The specific resistance value of the heat generating member used for the thermal printing head described above is generally beyond 4,000 xcexcxcexa9xc2x7cm eventually.
In accordance with the conventional art, therefore, there has been no heat generating member that may be adoptable for use of an ink jet recording head, which should be provided with an excellent response by short pulse driving, while presenting a high sheet resistance value.
Further, along with more precise images to be recorded, the size of heaters should be made smaller for recording by means of smaller droplets. As a result, as far as the conventional heat generating member is used, the electric current value is increased, leading to a problem related to heat generation after all.
Therefore, it is the main objective of the present invention to provide a substrate for use of an ink jet recording head having heat generating members, each being capable of solving all the problems described above, which are inherent in the conventional heat generating members of the ink jet recording head, and also, being capable of obtaining recorded images in high quality for a long time, as well as to provide an ink jet recording head and an ink jet recording apparatus.
It is another object of the invention to provide a substrate for use of an ink jet recording head having heat generating members, each being capable of discharging stably even when dots are made smaller for images to be recorded in high precision at higher speeds, and also, to provide an ink jet recording head, as well as an ink jet recording apparatus.
It is still another object of the invention to provide an ink jet pen including an ink reservoir unit for retaining ink to be supplied to such excellent ink jet recording head as described above, and also, to provide an ink jet recording apparatus provided with such ink jet recording head.
It is a further object of the invention to provide an ink jet recording head having an enhanced interlayer contactness for an ink jet recording head provided with a laminated structure of heat accumulation layer/heat generating resistance layer/protection layer having the heat generating resistance layer between them.
In order to achieve these objectives, the present invention is designed to provide a substrate for use of an ink jet recording head, an ink jet recording head, an ink jet recording apparatus, and a method for manufacturing them as given below.
In other words, a substrate for use of an ink jet recording head provided with a plurality of heat generating members for generating thermal energy to be utilized for discharging ink, wherein the heat generating members are structured by thin film formed by material represented by Tax Siy Rz having specific resistance value of 4000 xcexcxcexa9xc2x7cm or less, where R: one or more kinds of elements selected from among C, O, N, and x+y+z=100.
Also, an ink jet recording head provided with ink discharge openings for discharging ink, a plurality of heat generating members for generating thermal energy to be utilized for discharging ink, and ink flow paths including the heat generating members therein, at the same time being conductively connected with the ink discharge openings, wherein the heat generating members are structured by thin film formed by material represented by Tax Siy Rz having specific resistance value of 4000 xcexcxcexa9xc2x7cm or less.
Also, an ink jet recording apparatus provided with an ink jet recording head having ink discharge openings for discharging ink, a plurality of heat generating members for generating thermal energy to be utilized for discharging ink, and ink flow paths including the heat generating members therein, at the same time being conductively connected with the ink discharge openings, and carrier means for carrying a recording medium receiving ink to be discharged from the recording head of the ink jet recording head, wherein the heat generating members are structured by thin film formed by material represented by Tax Siy Rz having specific resistance value of 4000 xcexcxcexa9xc2x7cm or less.
Also, a method for manufacturing an ink jet recording head provided with ink discharge openings for discharging ink, a plurality of heat generating members for generating thermal energy to be utilized for discharging ink, and ink flow paths including the heat generating members therein, at the same time being conductively connected with the ink discharge openings, wherein the heat generating members use an alloy target formed by Taxe2x80x94Si, and by means of reactive sputtering system these members are formed in the mixed gas atmosphere having at least nitrogen gas, oxygen gas, carbon gas, and argon gas.
Also, a method for manufacturing an ink jet recording head provided with ink discharge openings for discharging ink, a plurality of heat generating members for generating thermal energy to be utilized for discharging ink, and ink flow paths including the heat generating members therein, at the same time being conductively connected with the ink discharge openings, wherein the heat generating members use two kinds of targets formed by Ta and Si, and by means of two-dimensional co-sputtering system these members are formed in the mixed gas atmosphere having at least nitrogen gas, oxygen gas, carbon gas, and argon gas.
With the provision of an ink jet recording head by means of structure and method of manufacture of the present invention, the heat generating members described above make it possible to obtain a desired durability even when the size of heaters is made smaller, while the heaters are driven by shorter pulses for a longer period of time, and demonstrate high energy efficiency in order to suppress heat generation for energy saving. At the same time, recorded images are provided in high quality.
Also, the present invention is not limited to only use of ink for ink jet recording head. The invention is also applicable to liquid for an ink jet recording head, which can be discharged by use of the heat generating members described above.